Necrosis of adipose tissue induced by sequential infections with unrelated viruses.

Vaccinia virus infection in mice previously infected with and immune to lymphocytic choriomeningitis virus resulted in a clinical illness which neither virus alone induced. The main pathologic finding was extensive fat necrosis with a cellular infiltrate suggestive of delayed type hypersensitivity. Vaccinia virus titers in adipose tissue of clinically ill mice were not higher than those in relevant control groups. This indicates that an unusual virus-induced disease can arise in an animal with a history of unrelated virus infection, and that this disease may be due to an altered host response to infection. The experimental model presented here suggests that chronic inflammation and necrosis of a given tissue may depend on sequential infection with two viruses, neither of which would be capable of inducing such a lesion.